Projectors are generally devices that integrate light sources, optics systems, electronics, and displays for front- or rear-projecting images from computers or video devices. Typical projectors include spatial light modulators (SLM's) to modulate light spatially, so that images are projected onto screens for viewing. Light is transmitted to an SLM, which processes the light so that the desired image pixel is projected onto a screen. The principle of operation of SLM's may be based on light reflection, light transmission, light interference, and/or another principle. There is typically one pixel on each SLM in the projector for each pixel of image data to be projected. Examples of SLM's include liquid crystal display (LCD) SLM's, diffractive light device (DLD) SLM's, and other types of SLM's. A DLD in particular is a kind of micro-electromechanical (MEM) device.
A number of SLM's corresponding to the pixels needed for a particular resolution are usually utilized within a projection system. If an SLM is defective, the pixel of image to which it corresponds within the projection system will not be properly projected. Therefore, testing of the SLM's of a given projection system is usually accomplished to ensure that the vast majority of them are not defective. However, some types of SLM's, especially those that are implemented as MEM devices, are difficult to test. For example, MEM devices, such as some kinds of DLD's, may be able to have signals electrically written thereto, but may not be able to have signals electrically read therefrom. As a result, testing of such MEM devices and the accompanying driver circuitry cannot be easily accomplished to ensure that the pixels to which they correspond will be properly projected.